There is a nice zen koan that has helped me put the "what ifs" out of my mind.
It is the story of a tortoise who asks a guru about his path. The guru says, "you must remember, you are not ONE person, you are THREE. The FIRST you, is the you of the past. The you that sometimes embarrasses you. The you that has made mistakes and some of them awful. But, along with the mistakes there has been accomplishments as well. It is the you that has brought you to the PRESENT you. The you, you are now. The you that must make decisions for the now, for the present. He cannot reach back to the past you. The past you is gone. The decisions that he made can not be undone because you are the result of THAT you.
What about the third me? What is he?
He is you in the FUTURE. The PRESENT you will have a large impact on the FUTURE you. So, forget your PAST you and build to make your FUTURE you what you would like to be in the PRESENT."